The 200 fairy lights are 3 wire but the 800 aren't. I bought the 800 a while back (before the sale ) for a "tune to" sign, it's 2 lots of 400 which wire to the transformer via a 'double adapter' (see pic). As I only needed just over 500 bulbs for the tune to sign I thought I'd get the 200 pack and add that in instead of the extra 400 lot. Turns out the 200 pack have completely different connector (see pic).

No idea what the 400 light pack has, guess you'd have to break open the pack (like I probably should have done with the 200 light pack)